<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <!-- <link rel="stylesheet" href="./bootstrap/css/bootstrap.min.css" /> -->
  </head>

  <body>
    <div id="app">
      <h2>Hello {{count}}</h2>
      <button @click="count++">count++</button>
    </div>
    <script type="module">
      import {
        createApp,
        ref,
        reactive,
        computed,
        watch,
      } from "./vue.esm-browser.js";
      const app = createApp({
        setup() {
          const count = ref(0);
          watch(
            count,
            (newCount, oldCount) => {
              console.log(newCount, oldCount);
            },
            {
              // deep:true,
              // immediate: true,
              once: true,
            }
          );

          return {
            count,
          };
        },
      });

      app.mount("#app"); //挂载
    </script>
  </body>
</html>
